In general, TFT liquid crystal panels utilize the active matrix addressing scheme in which liquid crystals are sealed between an array-side substrate having TFT devices built therein and a substrate having a color filter attached thereto, and voltages are controlled by the TFTs for controlling the alignment of liquid crystals.
For the manufacture of the array-side substrate, plural layers are repeatedly printed on a mother glass sheet of alkali-free glass by light exposure through original plates having circuitry pattern, known as large-size photomasks. The color filter-side substrate is similarly manufactured by a lithographic process, known as dye impregnation process.
For the manufacture of both array- and color filter-side substrates, large-size photomasks are necessary. To implement precision light exposure, synthetic quartz glass substrates having a low coefficient of linear expansion are often used for the large-size photomasks.
When the peripheral surface of a substrate is chamfered to any shape by means of a chamfering machine, dusting from the peripheral surface becomes one of factors that govern the surface state of a finished product, especially the presence or absence of contaminants on the surface. If the peripheral surface of the substrate is rough, the contaminants deposited on the peripheral surface cannot be removed by simple cleaning. Not only some contaminants migrate and deposit on the substrate major surfaces, which in turn, requires re-cleaning or re-polishing to remove those contaminants, leading to a drop of manufacture yield.
To solve the above and other problems, a method of mirror surface finishing the peripheral surface of a substrate of any shape is employed in the case of IC photomask substrates (see JP-A 56-46227). In the case of large-size substrates for LC, on the other hand, they are of varying sizes, which makes it difficult for a machine to handle substrates (because defects are formed on the surface if a machine component comes in contact with the surface). It is thus a common practice to manually hold the substrate by clamping at the peripheral surfaces by hands. A mirror finish if administered on the peripheral surface of a large-size substrate as in the case of IC photomask substrates, combined with the substantial weight of the large-size substrate, often causes slippage to occur between the handling gloves and the substrate, resulting in a failure to hold the substrate.
It would be desirable to have a large-size substrate which generates a minimum amount of dust during cleaning and allows manual handling.